Renewable power generation from forest residues is commonly practiced in the forest products industries. The U.S. forest products industry consumed 27.1 million tons of wood derived biomass, called “hog fuel”, in the generation of steam. By comparison, the power generation industry used 11.9 million tons of biomass of which 80% is wood derived. The biomass consumption in power generation is expected to double in every 10 years until 2030.
The major wood components are lignin, hemicelluloses and cellulose. The steam explosion process dissolves predominantly hemicelluloses in temperatures above 160° C. Hemicelluloses fraction removed in this process is termed “extract”. A concentration of the extract through evaporation is energy intensive, although it is currently practiced to produce molasses.
Previous research indicates that ethanol, acetic acid and their byproducts can be derived from the wood extract. Especially hardwood produces an extract rich in acetic acid and sugars as taught by Amidon et al. in (U.S. Patent Application No. 2007/0079944 A1, Apr. 12, 2007).
The current inventors, Retsina; et al.(U.S. Patent Filing No. 61/175,588) have previously described a steam extraction and hydrolysis process, in which an alkaline acetate product is concentrated in reverse osmosis membrane from evaporator condensate. The clean permeate is further recycled to the host mill to achieve zero effluent operation. Furthermore, the current inventors Retsina; et al. (U.S. Patent Application No. 61/219,764) have described the process integration of the waste heat to temper power boiler feed water.
The current inventors found an alternative method to produce fermented alcohol, ethanol or butanol, from biomass extraction using steam explosion, followed by vapor recompression evaporation, acid hydrolysis, fermentation and distillation. The present inventors have now developed a process, wherein the hemicelluloses in the power plant biomass extract can be converted to chemical products in an energy efficient process.